Gas turbine engines are used to power aircraft, watercraft, power generators, and the like. Gas turbine engines typically include a compressor, a combustor, and a turbine. The compressor compresses air drawn into the engine and delivers high pressure air to the combustor. In the combustor, fuel is mixed with the high pressure air and is ignited. Products of the combustion reaction in the combustor are directed into the turbine where work is extracted to drive the compressor and, sometimes, an output shaft. Left-over products of the combustion are exhausted out of the turbine and may provide thrust in some applications.
Compressors and turbines typically include alternating stages of static vane assemblies and rotating wheel assemblies. The rotating wheel assemblies include disks carrying blades around their outer edges. When the rotating wheel assemblies turn, tips of the blades move along blade tracks included in static shrouds that are arranged around the rotating wheel assemblies. Such static shrouds may be coupled to an engine case that surrounds the compressor, the combustor, and the turbine.
Some shrouds may be made up of a number of segments arranged circumferentially adjacent to one another to form a ring. Such shrouds sometimes include sealing elements between parts to block air from leaking through the shroud during operation of the gas turbine engine. Thus, more air is forced to pass over the blades included in the rotating wheel assemblies which extract work from the air.
Some shrouds positioned in the turbine may be exposed to high temperatures from products of the combustion reaction in the combustor. Such shrouds sometimes include components made from materials that have different coefficients of thermal expansion. Various gas turbine components, including shrouds, may be cooled using impingement heat transfer, which directs a stream of fluid such as air at a surface of a component to be cooled. Typically, the impingement is achieved by machining impingement holes in a relatively thin plate above the surface or component to be cooled.